Removing some fields from uprefix

[Zheng Lin Edwin Yeo]

Hi,

I'm using Solr 7.2.0, and I have this /extract handler in my solrconfig.xml

  <requestHandler name="/update/extract"
                  startup="lazy"
                  class="solr.extraction.ExtractingRequestHandler" >
    <lst name="defaults">
      <str name="xpath">/xhtml:html/xhtml:body/descendant:node()</str>
      <str name="capture">content</str>
      <str name="fmap.meta">attr_meta_</str>
      <str name="uprefix">attr_</str>
      <str name="lowernames">true</str>
      <str name="update.chain">dedupe</str>
    </lst>
  </requestHandler>

Understand that this <str name="uprefix">attr_</str> will cause all
generated fileds that aren't defined in the schema to be prefixed with
attr_

Is there any way that we can remove some of the fields, but keep the rest?
For example, I would like to remove attr_x_parsed_by.

Regards,
Edwin